Hemodynamic and catecholamine responses to laryngoscopy and tracheal intubation in patients with complete spinal cord injuries

BACKGROUND: Endotracheal intubation in patients undergoing general anesthesia often causes hypertension and tachycardia, which may be altered when the efferent sympathetic fiber to the cardiovascular system is interrupted. The aim of the current study was to investigate the effects of different levels of spinal cord injury on the cardiovascular responses to intubation. METHODS: Fifty-four patients with traumatic complete cord injuries requiring tracheal intubation were grouped into quadriplegics (above C7; n = 22), high paraplegics (T1-T4, n = 8), and low paraplegics (below T5, n = 24) according to the level of injury. Twenty patients without spinal injury served as controls. Arterial pressure, heart rate, and rhythm were recorded at intervals for up to 5 min after intubation. Plasma concentrations of catecholamines were also measured. RESULTS: The intubation increased the systolic blood pressure similarly in control, high-paraplegic, and low-paraplegic groups (P < 0.05), whereas it did not alter the blood pressure in the quadriplegic group. Heart rate was significantly increased in all groups; however, the magnitude was more pronounced in the high-paraplegic group (67%) than in the control (38%) and quadriplegic (33%) groups. Plasma concentrations of norepinephrine were significantly increased after intubation in all groups; however, values were lower in the quadriplegic group and higher in the low-paraplegic group compared with those in the control group. Incidence of arrhythmias did not differ among groups. CONCLUSIONS: The cardiovascular and plasma catecholamine changes associated with endotracheal intubation may differ according to the affected level in patients with complete spinal cord injuries.     

Gabapentin attenuates the pressor response to direct laryngoscopy and tracheal intubation

Background. Laryngoscopy and tracheal intubation increase bloodpressure and heart rate (HR). The aim of the present study wasto investigate the effect of gabapentin when given before operationon the haemodynamic responses to laryngoscopy and intubation. Methods. Forty-six patients undergoing abdominal hysterectomyfor benign disease were randomly allocated to receive gabapentin1600 mg or placebo capsules at 6 hourly intervals starting theday (noon) before surgery. Anaesthesia was induced with propofoland cis-atracurium. Systolic, diastolic arterial blood pressures(SAP, DAP) and heart rate (HR) were recorded before and afterthe anaesthetic and 0, 1, 3, 5 and 10 min after tracheal intubation. Results. SAP was significantly lower in the gabapentin vs thecontrol group 0, 1, 3, 5 and 10 min after intubation [128 (27)vs 165 (41), P=0.001, 121 (14) vs 148 (29), P=0.0001, 115 (13)vs 134 (24), P=0.002, 111 (12) vs 126 (19), P=0.004 and 108(12) vs 124 (17), P=0.001 respectively]. DAP also was lowerin the gabapentin group 0, 1, 3, and 10 min after intubation[81 (18) vs 104 (19), P=0.0001, 77 (9) vs 91 (16), P=0.001,71 (10) vs 84 (13), P=0.001 and 67 (10) vs 79 (12), P=0.004].HR did not differ between the two groups at any time [82 (11)vs 83 (15), 79 (10) vs 80 (12), 86 (17) vs 92 (10), 82 (11)vs 88 (10), 81 (12) vs 81 (11), 77 (13) vs 79 (13), and 75 (15)vs 78 (12)]. Conclusion. Gabapentin, under the present study design attenuatesthe pressor response but not the tachycardia associated withlaryngoscopy and tracheal intubation.     

Hemodynamic and catecholamine responses to laryngoscopy with vs. without endotracheal intubation

To study the relationship between the intensity of the stimulus exerted against the base of the tongue during direct laryngoscopy and the magnitude of associated hemodynamic and catecholamine responses, a study was conducted in 40 ASA I or II patients. Laryngoscopy lasting 40 s was performed with a size 3 Macintosh blade connected to a force-displacement transducer. The intensity of the stimulus exerted during laryngoscopy is expressed by the product of its average force (N) and duration (s) and given as impulse in Ns. Highly significant relationships were found between the impulse during laryngoscopy and the maximal hemodynamic and catecholamine responses. Also, when laryngoscopy was followed by orotracheal intubation, significant relationships were found with steeper slopes of the regression lines for systolic blood pressure, heart rate and plasma epinephrine concentrations. A more rapid regression of hemodynamic data was seen in intubated patients, whereas their plasma catecholamine concentrations regressed more slowly. The mechanisms of the responses to laryngoscopy and orotracheal intubation are proposed to be by somato-visceral reflexes. Stimulation of proprioceptors at the base of the tongue during laryngoscopy induces impulse-dependent increases of systemic blood pressure, heart rate and plasma catecholamine concentrations. Subsequent orotracheal intubation recruits additional receptors that elicit augmented hemodynamic and epinephrine responses as well as some vagal inhibition of the heart.     

Hemodynamic changes occurring with tracheal intubation by direct laryngoscopy compared with intubating laryngeal mask airway in adults: A randomized comparison trial

BackgroundHemodynamic changes are major problems due to general anesthesia. We designed a prospective randomized study to compare the hemodynamic responses due to direct laryngoscopy (DL) and intubating laryngeal mask airway (ILMA).MethodsSeventy adult ASA-I and ASA-II patients referred to anesthesia department were randomly divided into two groups: direct laryngoscopy (Macintosh laryngoscope) and ILMA. Systolic, diastolic and mean arterial blood pressure and heart rate were recorded at baseline, preintubation, 1, 3 and 5 min after intubation following intubation. Also some complications including sore throat, laryngospasm, hoarseness and cough were evaluated.ResultsMean age of studied patients in DL group (including 11 (31.4%) male) was 35.5 ± 12.2 and 35.5 ± 9 years old in ILMA group (including 16 (45.7%) male). There was no significant difference between two studied groups about measured hemodynamic indices (P < 0.05, CI = 95%). The results showed that the just difference between increment of diastolic blood pressure and mean arterial pressure after 5 min interval of two studied groups was significant (P = 0.04; P = 0.034). There was no significant difference between the number of patients with positive complications and those without them (P < 0.05).ConclusionLaryngoscoy through the intubating laryngeal mask airway was associated with lesser mean arterial pressure and diastolic blood pressure when compared to intubation by direct laryngoscope. Thus this technique seems to reduce hemodynamic response to tracheal intubation.     

Effects of lightwand (Trachlight) compared with direct laryngoscopy on circulatory responses to tracheal intubation

We compared the effects of the lightwand technique on circulatory responses to tracheal intubation with those of direct-vision laryngoscopy. Forty adult patients received propofol and vecuronium, and their lungs were ventilated for 2 min via a mask with 5% sevoflurane in oxygen, after which the trachea was intubated orally using either the lightwand (Trachlight, n = 20) or the Macintosh laryngoscope (n = 20). Maximum mean arterial pressure changes did not differ between groups during (lightwand group, 25 (SD 21) mm Hg vs laryngoscopy group, 23 (19) mm Hg) and after (21 (24) mm Hg vs 21 (16) mm Hg) tracheal intubation. Maximum heart rate changes were similar for groups during (16 (14) beat min-1 vs 16 (15) beat min-1) and after (2 (11) beat min-1 vs 7 (19) beat min-1) tracheal intubation. There were no differences between the lightwand technique and direct-vision laryngoscopy in changes in mean arterial pressure and heart rate during and after tracheal intubation. We conclude that the effects of the lightwand technique on circulatory responses to tracheal intubation were similar to those of direct-vision laryngoscopy.      

Cardiovascular responses to tracheal intubation: a comparison of direct laryngoscopy and fibreoptic intubation

The cardiovascular responses to tracheal intubation using a fibreoptic bronchoscope or Macintosh laryngoscope were compared in twenty in-patients and twenty day-stay patients. Within these groups patients were randomly allocated to direct laryngoscopic or fibreoptic bronchoscopic intubation. Arterial blood pressure, heart rate and arterial oxygen saturation were recorded before induction and at one-minute intervals until four minutes after intubation. In both groups both laryngoscopic and bronchoscopic intubation resulted in a significant rise in blood pressure and heart rate. At no stage was there a significant difference in mean blood pressure in either group, or in heart rate in the day-stay patients, between the different methods of intubation. In the in-patients mean heart rate was significantly higher in those patients intubated with the bronchoscope at three and four minutes after intubation. Time taken for intubation was significantly longer in those patients intubated with the bronchoscope. In no patient did the arterial oxygen saturation fall below 98%.     

Tracheal intubation following training with the GlideScope® compared to direct laryngoscopy

Tracheal intubation using direct laryngoscopy has a high failure rate when performed by untrained medical personnel. This study compares tracheal intubation following direct laryngoscopy by inexperienced medical students when initially trained by using either the GlideScope^®, a video assisted laryngoscope, or a rigid (Macintosh) laryngoscope. Forty‐two medical students with no previous experience in tracheal intubation were randomly divided into two equal groups to receive training with the GlideScope or with direct laryngoscopy. Subsequently, each medical student performed three consecutive intubations on patients with normal airways that were observed by a anaesthetist who was blinded to the training method. The rates of successful intubation were significantly higher in the Glidescope group after the first (48%), second (62%), and third (81%) intubations compared with the Macintosh group (14%, 14% and 33%; p = 0.043, 0.004 and 0.004, respectively). The mean (SD) times for the first, second, and third successful tracheal intubations were significantly shorter in the Glidescope group (59.3 (4.4) s, 56.6 (7.1) s and 50.1 (4.0) s) than the Macintosh group (70.7 (7.5) s, 73.7 (7.3) s and 67.6 (2.0) s; p = 0.006, 0.003 and 0.0001, respectively). Training with a video‐assisted device such as the GlideScope improves the success rate and time for tracheal intubation in patients with normal airways when this is performed by inexperienced individuals following a short training programme.     

Intravenous chloroprocaine attenuates hemodynamic changes associated with direct laryngoscopy and tracheal intubation

We compared the effects of an IV administration of chloroprocaine and lidocaine on circulatory responses associated with endotracheal intubation. Thirty patients were randomly allocated to receive normal saline (placebo), lidocaine (1.5 mg/kg), or preservative-free chloroprocaine (4.5 mg/kg) 45 s before endotracheal intubation. Blood pressures and heart rate and rhythm were recorded before laryngoscopy and at 0.5, 1, 1.5, 2, 3, and 5 min after intubation. Blood samples were analyzed for catecholamine and chloroprocaine concentrations. Chloroprocaine reduced increases in blood pressure in response to intubation when compared with patients receiving normal saline and lidocaine. Systolic blood pressures at 0.5 and 1 min after intubation were significantly lower in the chloroprocaine group when compared with both the control and lidocaine groups (P < 0.05). Diastolic and mean blood pressures were significantly lower in the chloroprocaine group at all time points until 5 min after intubation (P < 0.05). Chloroprocaine and, to a lesser degree, lidocaine, produced marked attenuation of intubation-induced increases in plasma concentration of epinephrine and norepinephrine. Plasma concentrations of norepinephrine were significantly smaller in the chloroprocaine group at 0.5, 1, and 1.5 min, and plasma concentrations of epinephrine were significantly smaller at 0.5 after intubation when compared with control and lidocaine groups (P < 0.05). Measurable concentrations of chloroprocaine were recorded in plasma samples for 2 min after its administration. No adverse chloroprocaine effects (i.e., circulatory disturbances, venous irritation) were detected. The IV administration of chloroprocaine effectively blunted cardiovascular response produced by laryngoscopy and endotracheal intubation, and this effect was more pronounced when compared with IV lidocaine.     

Attenuation of the pressor response to laryngoscopy and tracheal intubation with intravenous verapamil

This study was undertaken in surgical patients in order to evaluate the effects of intravenous verapamil on the circulatory responses to laryngoscopy and tracheal intubation. Laryngoscopy for tracheal intubation was initiated 1 min after thiamylal 5 mg.kg-1 and succinylcholine 1.5 mg.kg-1 in the control group (n = 21). The verapamil group (n = 23) received intravenous verapamil 0.1 mg.kg-1 immediately after thiamylal-succinylcholine administration. The resulting changes in mean arterial pressure (MAP) and heart rate (HR) were continuously measured. Compared with the control group, MAP increased less in response to laryngoscopy and tracheal intubation (56 +/- 13% versus 25 +/- 15% above baselines, P less than 0.01) and returned toward baseline sooner in patients receiving verapamil. For hypertensive patients, MAP increases from baseline after intubation were 18 +/- 9% in the verapamil group, and 53 +/- 14% in the control group, respectively (P less than 0.001). Increases in HR response to laryngoscopy for intubation were comparable in both groups. We conclude that intravenous verapamil is effective in reducing pressor responses during endotracheal intubation, especially in hypertensive patients.     

Evaluation of the cardiovascular responses to fiberoptic orotracheal intubation with television monitoring: comparison with conventional direct laryngoscopy

STUDY OBJECTIVE: To evaluate and compare cardiovascular responses to a new method of orotracheal intubation incorporating TV monitoring, with conventional orotracheal intubation via rigid blade laryngoscopy. DESIGN: Prospective single-blind study. SETTING: Operating room of a medical college hospital. PATIENTS: 90 ASA physical status I and II surgical patients requiring general anesthesia and orotracheal intubation. INTERVENTIONS: Patients were randomly allocated to two groups, one for the new intubation method and the other for conventional intubation using a rigid laryngoscope. In the new method, an anesthesiologist inserted an endotracheal tube alone into the trachea via TV monitoring through the bronchoscope, which was inserted by an assistant through the mouth to the middle larynx. The patient's trachea was intubated without extreme stretching of laryngeal tissues or deep insertion of the tip of the bronchoscope. In the conventional method, orotracheal intubation was performed with rigid direct laryngoscopy. MEASUREMENTS: Noninvasive blood pressure (BP) and heart rate (HR) were measured before arrival at the operating room, and before and after orotracheal intubation.Main Results: Although this method was expected to be a minimally invasive fiberoptic intubation technique, the patients showed significant increases in BP and HR. No significant differences between the two groups were observed in cardiovascular responses immediately after intubation: the systolic BP, 169.5 +/- 28.3 versus 167.0 +/- 23.1 mmHg, and HR, 100.2 +/- 18.2 versus 98.8 +/- 16.6 bpm. CONCLUSIONS: Insertion of an endotracheal tube may itself be the most invasive stimulus during intubation procedures.     

Facilitation of fiberoptic nasotracheal intubation by simultaneous direct laryngoscopy in anesthetized patients

Two cases of unexpected difficult intubation during induction of general anesthesia were reported. The first case, a 68-year-old male was scheduled for coronary artery bypass surgery. The second case, a 94-year-old male with senile dementia was arranged for exploratory laparotomy. Anesthesia was induced with diazepam 10 mg, fentanyl 30 micrograms/kg, and pancuronium 8 mg in the first case while in the second case fentanyl 100 micrograms, lidocaine 80 mg, thiopental 200 mg and succinylcholine 80 mg were used. In these two cases oral tracheal intubation with laryngoscope was unsuccessful. Assisted ventilation could be maintained via a face mask. With the help of direct laryngoscopy, fiberoptic bronchoscope-aided nasotracheal intubation was successfully achieved.